This invention relates to new image-formation systems wherein the photosensitive material is a nitrone and in which the image may be fixed by the use of heat. It is known to use nitrone in the formation of photographic images. In U.S. Pat. No. 2,426,894 nitrones are used in the production of images, but the method for fixing the image requires the use of aqueous washing procedures. The present system enables one to eliminate the necessity for aqueous washing and substitutes therefor heat treatment to fix the image.
In the process of the present invention, it is possible to use any photosensitive nitrone. A nitrone is an organic compound of the formula ##STR1## wherein R.sub.1 and R.sub.2 can be any alkyl or aryl group, R.sub.2 can be hydrogen, an alkyl or aryl group. R.sub.1, R.sub.2, and R.sub.3 may be substituted. The nitrones wherein R.sub.1 and R.sub.3 are aryl groups are particularly valuable because these compounds have ultraviolet absorption maxima in the photographically useful region of the spectrum, above 300 m.mu.. These may be represented by the formula RCH=N(.fwdarw.O)R', here R and R' are aryl groups, while certain other groups have been found likewise to be particularly beneficial as the R group in such nitrones.
It is highly to be desired to find a new, efficient system for the direct reproduction of images. The nitrone system produces a negative image of a positive. It is a reverse process, not a direct process, useful for example for the duplication of office correspondence, for the formation of microfilm records and so on. There are many commercial duplicating systems which are now in satisfactory operation, but most exhibit some undesirable characteristics. The diazo system requires either the use of aqueous developers, gaseous ammonia or a dry reagent that yields an alkaline material upon heating, which makes for a complicated process. The systems based on the use of sensitive silver salts are proportionately expensive. If the reproduction system is to be used to form microfilm copies, it is necessary for the system to be capable of excellent definition. The systems of the present invention are capable of finer definition than conventional silver halide/gelatin systems.